1. Field of the Invention
The invention relates to a fuel cell and a method of manufacturing the fuel cell, and, in particular, to a fuel cell that is less likely to suffer from a reduction in its power generating capability, and a method of manufacturing such a fuel cell.
2. Description of the Related Art
In recent years, fuel cells operable to generate electric power utilizing electrochemical reactions between hydrogen and oxygen receive widespread attention. One example of fuel cells has a laminated structure consisting principally of a membrane electrode assembly (which will be called “MEA” when appropriate); diffusion layers and separators, in which the diffusion layers are disposed on opposite major surfaces of the MEA, and the separators are disposed on major surfaces of the diffusion layers opposite to their major surfaces facing the MEA. The MEA may be constructed such that a cathode electrode layer is disposed on one of the opposite surfaces of the electrolyte layer, and an anode electrode layer is disposed on the other surface of the electrolyte layer. The diffusion layers are formed of, for example, a porous material.
In operation, air containing oxygen and a fuel gas containing hydrogen are supplied to the diffusion layers of the fuel cell via the separators. The air and fuel gas supplied to the fuel cell may also be called “reaction gas”. The reaction gas supplied to the diffusion layers of the fuel cell is then supplied to the MEA while flowing through the interior of the diffusion layers, so that the reaction gas is used for power generation in the MEA. Part of the reaction gas which was not used for power generation is discharged to the outside of the fuel cell via the diffusion layers and separators.
In order to prevent leakage of the reaction gas from the inside to the outside of the fuel cell, seal members may be provided which surround the peripheries of the MBA and diffusion layers, as disclosed in, for example, JP-A-2002-231274.
In the fuel cell as described above, the seal members and the diffusion layers are located with certain spacing provided therebetween, in order to prevent incomplete sealing and variations in the surface pressure due to interference between the seal members and the diffusion layers in the stacking direction of the fuel cell. As a result, some space is formed between the seal members and the diffusion layers. With this arrangement, part of the reaction gas supplied to the fuel cell may pass through the space, and may be discharged to the outside of the fuel cell without being used for power generation. If part of the reaction gas is discharged without being used for power generation, the power generating efficiency of the fuel cell may deteriorate.